A millimeter wave injection-locked frequency doubler

Abstract

The application discloses a kind of millimeter wave injection locking frequency doubler, including complementary push-push frequency doubler circuit and two parts of injection locking oscillator.Complementary push-push frequency doubler circuit is used to generate harmonic signal with frequency doubling, and injection locking oscillator is used to lock the harmonic generated by complementary push-push frequency doubler circuit, and complementary push-push frequency doubler circuit is directly coupled with injection locking oscillator and connected.The input fundamental wave signal generates harmonic component through complementary push-push frequency doubler circuit, and then directly coupled with injection locking oscillator to realize frequency doubling.Compared with the structure of traditional frequency doubler, the application still has a wide locking range when the input power is small, and has the advantages of low input sensitivity, low power consumption, high integration and the like.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency integration technology, and in particular to a millimeter wave injection-locked frequency doubler applied to a frequency synthesizer. Background Art

[0002] Frequency multipliers play a crucial role in phase-locked loops (PLLs) and are crucial circuits in wireless communication systems. Currently, most millimeter-wave PLLs utilize a low-frequency PLL cascaded with a frequency multiplier. This approach offers a good compromise between local oscillator phase noise and power consumption, while also preventing injection pulling in the oscillator's resonant cavity. Traditional frequency multipliers have a relatively narrow locking range, typically around 8%, limiting their application. Main methods for achieving a wide locking range include reducing the Q factor of the LC resonant cavity and increasing the injection efficiency of the second harmonic. However, reducing the Q factor of the LC resonant cavity reduces the parallel resistance of the cavity, necessitating an increase in the size of the negative resistance transistor and increasing power consumption. Increasing the injection efficiency of the second harmonic requires separate optimization of the injection stage circuitry, complicating the circuit structure. Therefore, expanding the frequency division range of the injection-locked doubler is a crucial requirement for designing high-quality high-frequency frequency multipliers.

[0003] The paper "MC Chen and CY Wu. Design and analysis of CMOS subharmonic injection-locked frequency triplers. IEEE Transactions on Microwave Theory and Techniques [J], 2008, 56(8): 1869–1878" uses a MOS direct injection structure, where the MOS transistor directly injects into the resonant cavity, and its drain generates high-order harmonic pulling and locks the resonant cavity frequency. Although this method of using MOS transistors for direct injection is simple in structure, it consumes a lot of power and cannot optimize the injection transistor, making it impossible to increase the injection signal and thus the locking range.

[0004] The document "H. Jia and L. Kuang. "A W-Band Injection-Locked Frequency Doubler Based on Top-Injected Coupled Resonator[J]. In: 2016 IEEE Transactions on Microwave Theory and Techniques. 210-218." adopts a top-injected coupled resonator-based way to realize a W-band injection-locked frequency doubler. The second harmonic current is injected from the top, which avoids the source stage degeneration problem, but the circuit design is relatively complex and requires a high Q value, which to some extent increases the circuit power consumption and cannot further increase the locking range of the circuit. SUMMARY

[0005] The present application aims to solve the problem of the small locking range of the injection-locked frequency doubler structure in the prior art.

[0006] Technical scheme: To achieve the above-mentioned application purpose, a millimeter wave injection-locked frequency doubler with a wide range of the present application comprises two parts of a complementary push-push frequency doubling generation circuit and an injection-locked oscillator, and the complementary push-push frequency doubling generation circuit is directly coupled with the injection-locked oscillator; the injection fundamental wave signal is injected through the positive input end and the negative input end of the complementary push-push frequency doubling generation circuit and the injection-locked oscillator, the injection fundamental wave signal generates a harmonic component through the complementary push-push frequency doubling generation circuit, and then is directly coupled to the injection-locked oscillator, the injection-locked oscillator locks the harmonic signal generated by the complementary push-push frequency doubling generation circuit, and generates a frequency doubling output signal.

[0007] The complementary push-push frequency doubling generation circuit comprises a first MOS tube, a second MOS tube, a third MOS tube, a fourth MOS tube, a fifth MOS tube and a sixth MOS tube; the gates of the first MOS tube and the second MOS tube are connected to the negative input end, and the gates of the third MOS tube and the fourth MOS tube are connected to the positive input end; one end of the drain of the first MOS tube and the fourth MOS tube is connected to the first inductor, and the other end of the drain of the second MOS tube and the third MOS tube is connected to the first inductor; the source of the first MOS tube and the fourth MOS tube is connected to the gate of the sixth MOS tube, and the source of the second MOS tube and the third MOS tube is connected to the gate of the fifth MOS tube.

[0008] The complementary push-push frequency doubling generation circuit adopts a completely symmetrical structure, so that the signal voltage swing of the source and the drain of the first MOS tube is approximately equal.

[0009] The injection-locked oscillator is composed of a first inductor, a first adjustable capacitor, a second adjustable capacitor, a tuning voltage, a seventh MOS tube and an eighth MOS tube; the drain of the seventh MOS tube and the drain of the eighth MOS tube are connected with the first adjustable capacitor and the second adjustable capacitor respectively; the gate of the eighth MOS tube is connected with the drain of the seventh MOS tube, and the gate of the seventh MOS tube is connected with the drain of the eighth MOS tube; the source of the seventh MOS tube and the source of the eighth MOS tube are connected with the ground, wherein the seventh MOS tube and the eighth MOS tube are used for negative resistance compensation.

[0010] The injection-locked oscillator, when the injection-locked oscillator is locked and the phase of the injection-locked oscillator at the frequency point is not zero, the complementary push-push frequency doubler circuit of the external circuit must provide sufficient phase to compensate for the phase difference between the total current flowing into the injection-locked oscillator and the free current of the injection-locked oscillator, so that the locking occurs; the phase difference between the total current flowing into the injection-locked oscillator and the free current of the injection-locked oscillator is related to the phase of the injection-locked oscillator impedance, so the injection-locked oscillator is adjusted so that the injection-locked oscillator impedance is flat enough to widen the locking range of the injection-locked frequency doubler.

[0011] The injection-locked oscillator, the total current flowing into the injection-locked oscillator can be regarded as the vector sum of the free oscillation current of the injection-locked oscillator and the injection current, and the angle between the vector total current and the free current of the injection-locked oscillator is the phase of the injection-locked oscillator input impedance; under the fixed power of the injection signal, the current generated by the complementary push-push frequency doubler circuit is a fixed value, and the maximum angle of the total current composed of the free current of the injection-locked oscillator and the current generated by the complementary push-push frequency doubler circuit determines the locking range; increasing the power of the external injection signal of the injection-locked oscillator can widen the working bandwidth of the injection-locked oscillator, and the power of the injection signal is increased in a direct coupling manner.

[0012] The frequency of the output signal is twice the frequency of the injection fundamental wave signal.

[0013] Beneficial effects: compared with the prior art, the millimeter wave injection-locked frequency doubler has the following beneficial effects:

[0014] 1. The problem of narrow locking range of the traditional injection-locked frequency doubler at low input power is solved, and a millimeter wave injection-locked frequency doubler with low input sensitivity is provided, so that the frequency doubler still has a wide locking range at low input power.

[0015] 2. The injection-locked frequency doubler works far from the locking edge under a given frequency offset by using the MOS tube to provide additional phase compensation, and the power of the injection signal is increased in a direct coupling manner, so as to expand the locking range and realize super-wide-range locking. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is the basic injection locking circuit schematic diagram;

[0017] Figure 2 is the current vector synthesis diagram of LC resonant cavity;

[0018] Figure 3 is the complementary push-push frequency doubler circuit schematic diagram of the present application;

[0019] Figure 4 is the millimeter wave injection locking frequency doubler with wide locking range of the present application.

[0020] In the figure: the first inductor L1, the first MOS transistor M1, the second MOS transistor M2, the first adjustable capacitor C1; the second inductor L2, the second inductor L3, the second adjustable capacitor C2, the third MOS transistor M3, the fourth MOS transistor M4, the fifth MOS transistor M5, the sixth MOS transistor M6, the seventh MOS transistor M7, the eighth MOS transistor M8, the first resistor R1, the second resistor R2, the third capacitor C3, the fourth capacitor C4, the positive input terminal f in+ , the negative input terminal f in- , the positive output terminal f out+ , the negative output terminal f out- , the power supply voltage VDD. DETAILED DESCRIPTION

[0021] The technical solutions of the present application will be described in detail below in combination with specific embodiments and the accompanying drawings.

[0022] As shown in Figure 1 , the basic injection locking circuit schematic diagram, the circuit structure includes: L1, C1 represents the inductance and capacitance of the resonant cavity, R P is the parasitic resistance of L1, the current source I inj represents the signal (double frequency signal) injected externally to the resonant cavity, I osc represents the free resonant current, I T is the vector superposition of I inj and I osc , ω inj is the frequency of the signal injected externally to the resonant cavity.

[0023] As shown in Figure 2 , the current vector synthesis diagram of LC resonant cavity, the circuit structure includes: the signal I inj injected externally to the resonant cavity, the free resonant current I osc , I T is the vector superposition of the above two currents, is the angle between the vector I T and the vector I osc , θ is the vector Iinj angle between the vector I osc and the vector I inj || is a fixed value, I osc is the maximum angle between the vector I inj and the vector I T . The maximum angle determines the locking range. Therefore, increasing the injection signal power can widen the working bandwidth of the injection-locked frequency doubler. The locking range expression is as follows:

[0024]

[0025] where ω0 is the free oscillation frequency of the injection-locked oscillator, and Q is the Q value of the corresponding LRC network, wherein the Q value can reflect the phase-frequency characteristic.

[0026] As shown in Figure 3 , 4 , the wide-locking-range millimeter wave injection-locked frequency doubler of the present application has a circuit structure comprising a complementary push-push frequency doubling generation circuit 1, an injection-locked oscillator 2, and an output buffer stage 3.

[0027] The complementary push-push frequency doubling generation circuit 1 is directly coupled to the injection-locked oscillator 2; the injection fundamental wave signal is injected through the positive input terminal f in+ and the negative input terminal f in- of the complementary push-push frequency doubling generation circuit 1 and the injection-locked oscillator 2. The injection fundamental wave signal generates harmonic components through the complementary push-push frequency doubling generation circuit 1, and then is directly coupled to the injection-locked oscillator 2. The injection-locked oscillator 2 locks the harmonic signal generated by the complementary push-push frequency doubling generation circuit 1 to generate a frequency-doubled output signal. The complementary push-push frequency doubling circuit 1 is used to generate a frequency-doubled harmonic signal, and the injection-locked oscillator is used to lock the harmonic signal generated by the harmonic generator. The complementary push-push frequency doubling circuit 1 generates harmonic components, and then is directly coupled to the injection-locked oscillator 2 to achieve frequency doubling. The complementary push-push frequency doubling generation circuit 1 comprises a first MOS transistor M1, a second MOS transistor M2, a third MOS transistor M3, and a fourth MOS transistor M4, the gate of the first MOS transistor M1 and the gate of the third MOS transistor M3 are connected to the negative input terminal f in- , the gate of the second MOS transistor M2 and the gate of the fourth MOS transistor M4 are connected to the positive input terminal f in+ . The drain of the first MOS transistor M1 and the drain of the fourth MOS transistor M4 output the second harmonic component of the preset frequency.

[0028] The injection locking oscillator 2 comprises a first coupling inductor L1, a first capacitor C1, a second capacitor C2, a seventh MOS transistor M7 and an eighth MOS transistor M8. The seventh MOS transistor M7 and the eighth MOS transistor M8 are negative resistance compensation. When the resonant cavity is locked and the phase of the resonant cavity at the frequency point is not zero, the external circuit (i.e. the complementary push-push double frequency generation circuit) must provide sufficient phase to compensate for the phase difference between the total current flowing into the resonant cavity and the free resonant cavity current, so that the locking occurs. According to vector analysis, it is easy to know that the phase difference between the total current flowing into the resonant cavity and the free resonant cavity current is related to the phase of the resonant cavity impedance, so adjusting the resonant cavity to make the resonant cavity impedance flat enough can widen the locking range of the injection locking double frequency generator.

[0029] The total current flowing into the resonant cavity can be considered as the vector sum of the free oscillation current of the oscillator and the injection current, and the angle between the total current vector and the free resonant cavity current is the phase of the LC resonant cavity input impedance. Under the fixed power of the injection signal, the current generated by the complementary push-push double frequency generation circuit is a fixed value, and the maximum angle of the total current composed of the free resonant cavity current and the current generated by the complementary push-push double frequency generation circuit determines the locking range. Therefore, increasing the injection signal power can widen the working bandwidth of the injection locking double frequency generator. Therefore, the design is also based on this idea, which increases the injection signal power through direct coupling.

[0030] The complementary push-push double frequency generation circuit 1 of the embodiment comprises a first MOS transistor M1, a second MOS transistor M2, a third MOS transistor M3 and a fourth MOS transistor M4. The harmonic generation circuit generates a second harmonic signal at the drain of the first MOS transistor M1 and the fourth MOS transistor M4 by using the nonlinearity of the first MOS transistor M1 and the fourth MOS transistor M4 to the input base frequency signal, and the drain current I d (t) can be expressed as follows

[0031]

[0032] where ω INJ is the frequency of the injection signal, k n = μ n C ox w n / l n and k p = μ p C ox w p / l p , C OX is the gate capacitance per unit area, w n / l n and w p / l pW / L n W / L p μn and μp are the electron and hole mobilities, respectively, and A is the amplitude of the differential input signal.

[0033] As mentioned above, the application has been described and represented with reference to particular preferred embodiments, but it is not to be interpreted as being limited to them. Various changes can be made in form and details without departing from the spirit and scope of the application, as defined in the appended claims.

Claims

1. A millimeter wave injection locked frequency doubler, characterized by, Complementary push-push double frequency generation circuit (1) and injection locking oscillator (2) two parts, complementary push-push double frequency generation circuit (1) and injection locking oscillator (2) are directly coupled; the injection base signal is injected through the positive input end ( f in+ ) and the negative input end ( f in- ) of the complementary push-push double frequency generation circuit (1) and the injection locking oscillator (2), the injection base signal generates harmonic components through the complementary push-push double frequency generation circuit (1), and then is directly coupled to the injection locking oscillator (2), the injection locking oscillator (2) locks the harmonic signal generated by the complementary push-push double frequency generation circuit (1), and generates a frequency multiplication output signal; The complementary push-push frequency doubling generation circuit (1) comprises a first MOS transistor (M1), a second MOS transistor (M2), a third MOS transistor (M3), a fourth MOS transistor (M4), a fifth MOS transistor (M5) and a sixth MOS transistor (M6); the gates of the first MOS transistor (M1) and the second MOS transistor (M2) are connected to a negative input end (V-) f in- ), the gates of the third MOS transistor (M3) and the fourth MOS transistor (M4) are connected to a positive input end (V+) f in+ ); the drains of the first MOS transistor (M1) and the fourth MOS transistor (M4) are connected to one end of a first inductor (L1), the drains of the second MOS transistor (M2) and the third MOS transistor (M3) are connected to the other end of the first inductor (L1); the sources of the first MOS transistor (M1) and the fourth MOS transistor (M4) are connected to the gate of the sixth MOS transistor (M6), and the sources of the second MOS transistor (M2) and the third MOS transistor (M3) are connected to the gate of the fifth MOS transistor (M5).

2. The millimeter wave injection locked frequency doubler of claim 1, wherein, The complementary push-push frequency doubling generation circuit (1) has a completely symmetrical structure, so that the signal voltage swing of the source and the drain of the first MOS transistor (M1) is approximately equal.

3. The millimeter wave injection locked frequency doubler of claim 1, wherein, The injection locking oscillator (2) is composed of a first inductor (L1), a first adjustable capacitor (C1), a second adjustable capacitor (C2), a tuning voltage (V tune ), a seventh MOS transistor (M7) and an eighth MOS transistor (M8); the drain of the seventh MOS transistor (M7) and the drain of the eighth MOS transistor (M8) are connected with the first adjustable capacitor (C1) and the second adjustable capacitor (C2) respectively; the gate of the eighth MOS transistor (M8) is connected with the drain of the seventh MOS transistor (M7), and the gate of the seventh MOS transistor (M7) is connected with the drain of the eighth MOS transistor (M8); the source of the seventh MOS transistor (M7) and the source of the eighth MOS transistor (M8) are both connected with the ground (GND), wherein the seventh MOS transistor (M7) and the eighth MOS transistor (M8) are used for negative resistance compensation.

4. The millimeter wave injection locked frequency doubler of claim 3, wherein, The injection locking oscillator (2) is locked when the phase of the injection locking oscillator is not zero at the frequency of the injection locking oscillator. The complementary push-push frequency doubling generation circuit (1) of the external circuit must provide sufficient phase to compensate for the phase difference between the total current flowing into the injection locking oscillator and the free current of the injection locking oscillator, so that the locking occurs. The phase difference between the total current flowing into the injection locking oscillator and the free current of the injection locking oscillator is related to the phase of the impedance of the injection locking oscillator, so adjusting the injection locking oscillator to make the impedance of the injection locking oscillator flat enough can widen the locking range of the injection locking frequency doubler.

5. The millimeter wave injection locked frequency doubler of claim 4, wherein, The total current flowing into the injection locking oscillator (2) is considered to be obtained by adding the free oscillation current of the injection locking oscillator and the injection current vector. The angle between the vector total current and the free current of the injection locking oscillator is the phase of the input impedance of the injection locking oscillator. Under the condition of a fixed power injection signal, the current generated by the complementary push-push frequency doubling circuit is a fixed value, and the maximum angle of the total current composed of the free current of the injection locking oscillator and the current generated by the complementary push-push frequency doubling circuit determines the locking range. Increasing the power of the external injection signal of the injection locking oscillator can widen the working bandwidth of the injection locking oscillator, and the power of the injection signal is increased through direct coupling.

6. The millimeter-wave injection locked frequency doubler of claim 1, wherein, The frequency of the output signal is twice the frequency of the injection fundamental signal.

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